PROJECT SUMMARY/ABSTRACT This is an application for a K08 Career Development Award for Gal Finer, MD, PhD, an Assistant Professor at the Feinberg School of Medicine of Northwestern University. This applicant has clinical training in Pediatric Nephrology and research training in immunology, genetics, and molecular biology. Her long-term career goal is to become an independently funded researcher with expertise in renal development. This proposal will position the applicant to gain advanced skills in developmental biology and pertinent experimental methods. To achieve these goals, Dr. Finer has assembled a multidisciplinary mentoring team with expertise in extramurally funded research, and she will be participating in coursework, seminars, and conferences. The broad, long-term objectives of the project included in this career development award are to decipher the molecular mechanisms that cause congenital anomalies of the kidney and urinary tract (CAKUT) and to identify novel therapeutic targets. CAKUT is the leading cause of chronic kidney disease in the first three decades of life and is associated with survival rate that is 30 times lower than that of healthy children. However, very little is known about the pathogenesis of CAKUT, and in the absence of prevention or curative treatment, care relies mainly on dialysis and transplantation. The nephron progenitor cells (NPCs) are multipotent cells that are critical for ensuring normal nephron number and normal kidney size at birth. It has been shown that, in normal development, these cells strike a balance between self-renewal and lineage-specific differentiation (NPC dynamics). However, the basic mechanisms that control these ?stem-like? cells are poorly understood. The Quaggin lab has identified a novel bHLH transcription factor, Tcf21, that is critical for kidney development. We preliminary show that Tcf21 controls the expression of Cited1 and Wnt4, two ?-catenin targets that are involved in NPC self-renewal and differentiation. The central hypothesis of this proposal is that Tcf21 controls NPC dynamics by regulating Wnt/?-catenin signaling. We will utilize unique genetic mouse models of Tcf21- depleted NPCs that present CAKUT-spectrum renal dysplasia to dissociate the effects of Tcf21 on NPC differentiation. Our Specific Aims are to decipher the molecular mechanisms by which Tcf21 regulates NPCs. To address our aims, we will perform molecular analysis of the ?-catenin pathway, analysis of genetic breeding, morphological analysis of the nephrogenic niche, lineage tracing, and single-cell RNA-sequencing. This work will be mentored by Dr. Susan Quaggin, Head of the Division of Nephrology and Hypertension and the Director of the Feinberg School Cardiovascular and Renal Institute at Northwestern University. Dr. Quaggin is an internationally acclaimed developmental nephrologist with extensive mentoring experience. The single-cell RNA analysis of this proposal will be mentored by Dr. Deborah Winter for her expertise in computational biology and bioinformatics in genomic studies. This project will also benefit from the exceptional research environment of Dr. Quaggin?s lab and the Northwestern University Feinberg School of Medicine.